<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        article{
            width:500px;
            background-color: #ccc;
            margin:0 auto;
            overflow:hidden;/*衍生用法，直接拿子元素的属性来设定*/
        }
        article div{
            width:100px;
            height:100px;
            background-color:red;
            margin:10px;
            float:left;
        }
    </style>
</head>
<body>
    <article>
        <div></div>
        <div></div>
        <div></div>
    </article>
</body>
</html>